1. Field of the Invention
The present invention relates to a bumper absorber for protecting pedestrians, and more particularly, to a bumper absorber for protecting pedestrians at the time of collision when a pedestrian is hit by a vehicle such as an automobile.
2. Background Art
Conventionally, it has been known that a bumper absorber for a vehicle such as an automobile is structured such that an energy absorber made of a foam is formed into a substantially I-shaped cross-sectional configuration, which aims both to protect pedestrians and to realize a level of performance which is traditionally demanded of a bumper (for example, Japanese Patent Application Laid-Open No. 60-37457).
However, with the aforementioned bumper absorber, when a load is applied from a vehicle front to the bumper absorber at a time of collision, an upper wall portion and a lower wall portion of the energy absorber having a substantially I-shaped cross-sectional configuration are compressed and deformed into a vehicle longitudinal direction. As a result, a rise in the initial load level is subdued, and the amount of energy absorbed decreases.
Therefore, a bumper absorber for protecting pedestrians is desirable in which a load level rises immediately at an initial stage when a load is applied to the bumper absorber, that is, when a pedestrian is hit by a bumper.
In another type of conventional bumper absorber, as shown in FIG. 28, a bumper absorber (also referred to as an “energy absorber”) 104 is housed in a bumper cover 102 (also referred to as a “shell”) of a bumper 100. The bumper absorber 104, as seen from a direction which is orthogonal to a longitudinal direction of the bumper absorber 104, is formed into a lopsided U-shaped cross-sectional configuration in which an opening portion 106 is formed to face a vehicle front. The bumper absorber 104 is also provided with a vehicle rear portion 104A in which a plurality of convex portions 108 is formed to face a vehicle rear and the vehicle rear portion 104A is fixed to a bumper reinforcement (also referred to as a “mounting means”) 110 (for example, JP-A No. 57-47234).
However, with the aforementioned bumper absorber 104, when, at the time of a collision, a load is applied from the vehicle front to the bumper absorber 104, as shown by a chain double-dashed line in FIG. 28, an upper wall portion 104B and a lower wall portion 104C of the bumper absorber 104 are compressed and deformed in a vehicle longitudinal direction. As a result, in direct relation to the rate of compression at which the bumper absorber 104 is compressed, there is a proportionate rise in impact load applied by the bumper absorber 104 on a pedestrian hit by the bumper.
In view of the aforementioned facts, an object of the present invention is to provide a bumper absorber for protecting pedestrians in which a load level can be swiftly raised at an initial stage when a load is applied to the bumper absorber, that is, when a pedestrian is hit by a bumper and in which a rise in an impact load acting on a pedestrian who is hit by the bumper can also be controlled.